Roller for flexographic printing presses and the like



T. CONNELLY Oct. 12, 1965 ROLLER FOR FLEXOGRAPHIC PRINTING PRESSES AND THE LIKE Filed March 25, 1964 FIG 4 INVENTOR. Thomas Gonna/[y Afiys.

3,210,826 ROLLER FOR FLEXOGRAPHTC PRINTING PRESSES AND THE LIKE Thomas Connolly, Joliet, llll., assignor to Tom Connelly, Inc, ioliet, ML, a corporation of Illinois Filed Mar. 25, 1%4, Ser. No. 354,569 4 Claims. (Cl. 29-429) The present invention relates generally to rollers for printing presses and, more particularly, to an improved roller having an outer surface adapted to carry printing plates in flexographic printing presses and the like.

It is a primary object of the present invention to provide a novel flexographic printing roller having an improved strength-weight ratio. Thus, it is an object of the invention to provide an improved roller which is lighter in weight than conventional flexographic printing rollers, and yet has suflicient strength to prevent flexing or other distortion of the roller surface even under rigorous operating conditions. A related object is to provide such a roller which is capable of absorbing various stresses encountered during operation Without flexing the surface of the roller which carries the printing plates, thereby insuring uniform, high quality printing.

It is another object of this invention to provide an improved flexographic printing roller which is so light in weight that it can be handled by a single man. A connected object is to provide such a roller which lowers shipping costs and reduces the load on the journal bearings which carry the roller in the printing press.

A further object of the invention is to provide an improved flexographic printing roller which has improved dependability and dimensional and thermal stability over extended operating periods. Thus, it is an object to provide such a roller which is not affected by the various liquids and atmospheric conditions encountered in use and, therefore, requires practically no maintenance.

It is a still further object of the invention to provide an improved roller construction which is easily adapted to manufacture by casting without the production of blowholes which mar the roller surface. Another object is to provide such a roller which is easily adapted to proper balancing prior to its installation in the printing press.

Other objects and advantages of the invention will become apparent upon reading the following description and appended claims and upon reference to the drawings, in which:

FIG. 1 is a perspective view of an improved printing roller embodying the present invention and adapted to carry printing plates in a flexographic printing press;

FIG. 2 is an enlarged sectional side view taken through the center of the roller of FIG. 1 with certain broken transverse segments of the roller being removed as indicated;

FIG. 3 is a sectional end view taken along line 33 in FIG. 2 but showing the complete cross section of the roller; and

FIG. 4 is a sectional end view taken along line 4-4 in FIG. 2 but showing the complete cross section of the roller.

While the invention will be described in connection with a preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, it is intended to cover the various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Turning now to the drawings, there is shown a cylindrically shaped printing roller 10 having a smooth outer surface adapted to carry the desired printing plates (not shown), which are usually made of rubber or polyethylene, used in flexographic printing. For the purpose of mounting the roller 10 in the supporting journal bearings nited States Patent provided in a flexographic printing press, a pair of axially aligned stub shafts 12 are secured to opposite ends of the main cylinder 11, each shaft having a spindle portion 13 at its outer end adapted to be journaled in the press. The cylinder 11 is preferably made of a light metal, such as aluminum or magnesium, in order to minimize the weight of the roller and to avoid corrosion problems.

In carrying out the present invention, there is provided an improved roller including a cylinder which is hollow and light in weight, and yet is internally constructed such that it has suflicient strength to prevent flexing or other distortion of the roller surface. Thus, the cylinder is provided with walls which are thin relative to the diameter of the cylinder, and a hollow sleeve having an outside diameter less than the inside diameter of the cylinder is arranged concentrically within the cylinder, the sleeve being substantially coextensive in length with the main cylinder. To facilitate prevention of flexing of the roller, an annular spacer member is disposed within the hollow cylinder such that the outer periphery of the spacer engages the inner periphery of the hollow cylinder and the inner periphery of the spacer engages the outer periphery of the hollow sleeve. Thus, referring to FIGS. 2-4, the cylinder 11 is made of a hollow aluminum casting having relatively thin walls as compared with the diameter of the cylinder, and defining a central cavity 15 within the casting so as to provide a uniform wall thickness around the entire circumference of the cylinder 11. The end walls 11a of the cylinder are preferably of equal thickness with respect to each other, but are somewhat thicker than the side walls 11b of the cylinder.

For the purpose of facilitating the prevention of flexing of the cylinder 11 during printing, the cylinder 11 is provided with an annular supporting rib 16 which projects from the inner surface of the cylinder 11 into engagement with a hollow metal sleeve 17 fitted concentrically within the cylinder 11. The sleeve 17 is substantially coextensive in length with the cylinder 11 and is in mechanical engagement with the end walls 11a of the cylinder. To insure proper balance of the roller, the annular spacer member or rib 16 is preferably positioned exactly midway between the cylinder ends 11a. Thus, the cylinder 11 is supported by the sleeve 17 at three equally spaced contact points, one at each end of the sleeve 17 and one at its midpoint. The ends of the sleeve 17 are preferably flared as shown in FIG. 2 in order to facilitate alignment of the stub shafts 12 with the sleeve 17 prior to welding the stub shafts to the sleeve.

It is believed that the hollow sleeve 17 is, by reason of its much smaller diameter, less rigid than the cylinder 11 so that the sleeve 17 in effect absorbs at least part of the flexing stresses and thereby aids in preventing flexing of the cylinder surface which carries the printing plates. It will be understood that the desired differential in rigidity between the sleeve 17 and the cylinder 11 may be attained by the selection of different materials and relative dimensions for the two members. For example, in the case of a cast aluminum cylinder having a /;-inch wall thickness and an outside diameter of about 4 to 12 inches, the sleeve 17 may be a 2-inch diameter l6-gauge steel pipe. The axial thickness of the rib 16 is not critical, a thickness of about one to two inches being suitable for most rollers. The rib may be formed as an integral part of the cylinder 11 or may be preformed and positioned within the mold along with the sleeve 17 prior to casting the cylinder 11.

For the purpose of illustrating the significant advantages achieved by this invention, it has been found that if a roller constructed according to the invention, thirty inches long with an outside diameter of 5.5 inches, is subjected to a flex test with a 50-pound pull, the roller exhibits no measurable flexing. By contrast, conventional rollers subjected to the same loading conditions exhibit enough measurable flexing to render them undesirable in the operation of high-speed fiexographic type printing presses.

In most fiexographic printing presses, the roller drive is applied to the journal means at only one end of the roller. In this connection, it will be appreciated that although the lightweight roller of this invention employs stub shafts as the journal means so that there is no solid shaft connecting the two journal means at opposite ends of the roller, the combination of the rib 16 with the cylinder 11 and the sleeve 17 provides an effective torque transmission system between the two journal means. This tends to equalize the stresses on the two stub shafts thereby prolonging the life of the journal system.

As can be seen in FIG. 2, the cylinder 11 and the sleeve 17 form a relatively large annular cavity 15 between the outer surface of the sleeve 17 and the inner surface of the cylinder 11. By reason of this hollow construction, the weight of the cylinder is not only reduced, but the casting of the cylinder 11 can also be facilitated. Thus, in order to cast the cylinder 11 from hot aluminum for example, the sleeve 17 and the stub shafts 12 are welded together as at 21a, and mounted in the appropriate mold. A thin metal liner 19, such as stovepipe for example, is then placed around the sleeve 17 with annular metal flanges 19a bearing against the sleeve 17 at each end of the liner 19, thereby forming the desired cavity 15. Finally, the hot aluminum is poured into the mold to form the cylinder 11, solidified by cooling, and removed. As the hot aluminum is poured into the mold, the gases within the sleeve 17 and the liner 19 are expanded by the heat and attempt to escape through the molten metal, thereby except for the features of the instant invention producing blowholes and other defects in the final cylinder. In this invention, these defects may be avoided by providing a plurality of vent holes 20 in the tube 17 and a small vent pipe 21 in the end of the cylinder 11. The expanding gases are then vented from the sleeve 17 into the cavity 15 where they are exhausted through the pipe 21, thereby effectively preventing the production of any blowholes. After the cylinder 11 has solidified, the vent pipe 21 is filled with aluminum or other material substantially the same weight.

For the purpose of keying or locking the cylinder 11 to the two stub shafts 12, a small peripheral notch or groove 12a is formed in that portion of each stub shaft which is fitted within the cylinder end walls 11a. These grooves 12a are then filled with molten aluminum as the cylinder 11 is cast and, after the metal has solidified, the stub shafts are firmly keyed to the metal cylinder 11. Alternatively, a plurality of small holes may be substituted for the grooves 12a.

In accordance with one feature of this invention, certain ratios are maintained between various dimensions of the roller element so as to achieve the optimum strength-weight ratio. Thus, the ratio of the radial distance between the sleeve 17 and the cylinder 11, to the outside diameter of the sleeve 17 should be between about 0.25 and about 2.5. Similarly, the ratio of the wall thickness of the cylinder 11 to the outside diameter of the cylinder 11 should be between about 0.05 and about 0.20. It has been found that dimensions within these ratio ranges provide a roller with a strength-weight ratio surpassing conventional printing rollers.

The construction of the roller which includes the metal liner 19 is useful not only in the casting of the roller, but also in the subsequent balancing of the roller before it is put into operation. Thus, if the roller is out of balance and it is desired to increase the weight of the cylinder 11 at a particular point, a hole is drilled through the cylinder 11 at that point, but not through the liner 19. The liner is then pushed inwardly at the end of the hole so as to form a small pocket between the cylinder 11 and the liner 19, and an appropriate amount of solder or other molten metal is poured into the hole so as to fill both the pocket and the hole. Thus, it is possible to increase the weight of the cylinder at the exact position and by the exact amount required for proper balance.

While the present invention has been described with particular reference to a roller having only one annular supporting rib, it will be understood that the invention is equally applicable to rollers having a plurality of rollers, as long as the ribs are equally spaced to provide a balanced construction.

What is claimed is:

1. A roller for a fiexographic printing press comprising, in combination, a closed hollow cylinder made of a light metal and having walls which are thin relative to the diameter of the cylinder, a hollow cylindrical sleeve fitted concentrically within said cylinder so as to define an annular cavity between said sleeve and the inner surface of said cylinder with the ends of said sleeve being joined to the end walls of said cylinder, a thin metal liner covering the inner surface of said cylinder including the end walls thereof, and journal means including a pair of stub shafts axially alined in opposite ends of said sleeve for rotatably mounting the roller.

2. A roller for a fiexographic printing press comprising, in combination, a closed hollow cylinder made of a light metal and having walls which are thin relative to the diameter of the cylinder, a hollow cylindrical sleeve fitted concentrically within said cylinder so as to define an annular cavity between said sleeve and the inner surface of said cylinder with the ends of said sleeve being joined to the end walls of said cylinder, an annular spacer member disposed within the annular cavity substantially midway between the ends of said cylinder and extending from the inner surface of said cylinder into engagement with the outer periphery of said hollow sleeve so as to facilitate prevention of flexing of the roller, a thin metal liner covering the inner surface of said cylinder including the end walls thereof and the opposed surfaces of said annular spacer member, and journal means including a pair of stub shafts axially alined in opposite ends of said sleeve for rotatably mounting the roller, said stub shafts including peripheral grooves cooperating with the cylinder end walls for keying the shafts to the cylinder.

3. A roller for a fiexographic printing press as defined in claim 2 in which the wall of the cylinder has a passage communicating between the annular cavity and the outside of the cylinder for venting gases from the cavity to the atmosphere.

4. A roller for a fiexographic printing press as defined in claim 3 in which the hollow sleeve has a passage formed therein for venting gases from the interior of the sleeve into the annular cavity between the sleeve and the cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,582,453 4/26 Dustan l0l-375 1,643,145 9/27 Winkler 29-130 X 1,759,192 5/30 Fulk 101375 1,906,738 5/33 Carroll. 2,949,852 8/60 Schaefer 101375 WALTER A. SCHEEL, Primary Examiner, LOUIS O, MAASSEL, Examiner. 

1. A ROLLER FOR A FLEXOGRAPHIC PRINTING PRESS COMPRISING, IN COMBINATION, A CLOSED HOLLOW CYLINDER MADE OF A LIGHT METAL AND HAVING WALLS WHICH ARE THIN RELATIVE TO THE DIAMETER OF THE CYLINDER, A HOLLOW CYLINDRICAL SLEEVE FITTED CONCENTRICALLY WITHIN SAID CYLINDER SO AS TO DEFINE AN ANNULAR CAVITY BETWEEN SAID SLEEVE AND THE INNER SURFACE OF SAID CYLINDER WITH THE ENDS OF SAID SLEEVE BEING JOINED TO THE END WALLS OF SAID CYLINDER, A THIN METAL LINER COVERING THE INNER SURFACE OF SAID CYLINDER INCLUDING THE END WALLS THEREOF, AND JOURNAL MEANS INCLUDING A PAIR OF STUB SHAFTS AXIALLY ALINED IN OPPOSITE ENDS OF SAID SLEEVE FOR ROTATABLY MOUNTING THE ROLLER. 